1. Field of the Invention
The present invention relates to a solid-state image capturing apparatus, a driving method of the solid-state image capturing apparatus, and an electronic information device. In particular, the present invention relates to a solid-state image capturing apparatus, in which a charge transferring direction of a horizontal transfer section is configured to be reversed on both sides of a predetermined position; a driving method of the solid-state image capturing apparatus; and an electronic information device.
2. Description of the Related Art
In general, a solid-state image capturing apparatus transfers electric charges generated by photoelectric conversions in a plurality of pixel sections (also simply referred to as a pixel, hereinafter) arranged in a two dimensional array by a vertical transfer section corresponding to each pixel section column in the vertical direction for each individual pixel section. The solid-state image capturing apparatus subsequently transfers the electric charges from the vertical transfer section by a horizontal transfer section, which is positioned at one end side of the vertical transfer section, to the horizontal direction for each line to be sent to an output section, and the solid-state image capturing apparatus outputs the electric charges as image capturing signals from the output section.
When capturing a video, the transferring of an electric charge from a light receiving section (pixel section) to an output section needs to be completed within a certain period of time in accordance with a frame rate, and the transferring of an electric charge requires a sufficient period of time so as not to cause deterioration due to the transferring. Therefore, it is required for a period of time for both the vertical transfer and the horizontal transfer to be set in view of the efficiency of the transfer.
In addition, a common solid-state image capturing apparatus has a configuration in which electric charges of all the effective pixels are transferred in the vertical direction, and subsequently, the electric charges are transferred in the horizontal direction to be sent to an output section. Therefore, such a solid-state image capturing apparatus is required for transferring electric charges with the same amount of time for all the effective pixels or for electric charges of a pixel of one frame even when the number of pixels required for capturing an image is smaller than the number of effective pixels.
For such a problem, Reference 1 discloses a method for, by providing a horizontal CCD drain gate between a horizontal CCD, which is a horizontal charge transfer section, and a horizontal CCD drain positioned near the horizontal CCD along the transfer direction, sweeping out unnecessary electric charges at once from the horizontal CCD to the horizontal CCD drain.
FIG. 9 is a diagram illustrating a method disclosed in Reference 1 described above, which illustrates a solid-state image capturing apparatus according to this method.
A solid-state image capturing apparatus 200 includes: a plurality of pixel sections 1 positioned in a matrix for photoelectrically converting an incident light into a signal charge; a vertical transfer section 2 for reading out the signal charge stored in each of the pixel sections 1 to transfer it in a column direction (vertical direction); a horizontal transfer section 3 for transferring the signal charge from the vertical transfer section 2 in a row direction (horizontal direction); and an output section 4 for amplifying the transferred signal charge and outputting it as an image capturing signal. Herein, the vertical transfer section 2 described above is positioned for each column of pixel sections and along each column of pixel sections, and the horizontal transfer section 3 described above is positioned at one end side of the vertical transfer section 2. In addition, a horizontal sweeping drain 6 is positioned on the opposite side of the horizontal transfer section 3 from a positional area of the pixel section described above, and a horizontal CCD drain gate 24 is positioned between the horizontal sweeping drain 6 and the horizontal transfer section 3. In addition, a vertical sweeping drain 5 is positioned on the opposite end of the vertical transfer section 2 described above.
Next, an operation will be described.
Herein, the center portion of the effective pixel area (i.e., area having pixel sections arranged in a matrix therein) in the solid-state image capturing apparatus is defined as a desirable image cutting out area 25. Therefore, electric charges generated in areas A and B are unnecessary electric charges, the area A being positioned above the upper end position of the pixel cutting out area 25 and the area B being positioned below the lower end position of the pixel cutting out area 25. Similarly, electric charges generated in areas C and D are unnecessary electric charges, the areas C and D being positioned on the left and right sides of the pixel cutting out area 25.
According to the conventional technique, when the unnecessary electric charges generated in the areas A and B are vertically transferred, the horizontal CCD drain gate 24 is turned on, and the unnecessary electric charges transferred to the horizontal transfer section 3 is drained to the horizontal sweeping drain 6 without being transferred in the horizontal direction. Further, unnecessary electric charges generated in the areas C and D and electric charges for one line including necessary electric charges generated in the desired pixel cutting out area 25, are vertically transferred to the horizontal transfer section. Subsequently, when the electric charges transferred in the horizontal transfer section is horizontally transferred, necessary electric charges 20 generated in the desirable pixel cutting out area 25 are transferred to the output section 4 subsequent to unnecessary electric charges 21 generated in the area C, and the horizontal CCD drain gate 24 is turned on to drain the unnecessary electric charges to the horizontal sweeping drain 6. As a result, among all the electric charges generated in the entire effective pixels of an image capturing element, unnecessary electric charges are thrown away, making it possible to reduce a driving frequency of a horizontal CCD functioning as a horizontal transfer section.    Reference 1: Japanese Laid-Open Publication No. 11-8801